Is my homepage calling posts wrongly? Css broken?

The problem in this highly customized theme is that column or div width in first page (homepage) has something wrong. Image and text area is not as wide as in actual post and as it is defined in CSS.

But if you click in to some post page like this one:
http://www.sitruunapuu.net/blog/2010/06/kaksi-sisaan-nelja-ulos/

You can see how it is meant to be (post margins widths ok and image width 500px and signature ‘sitruunapuu.net’ at lower right corner shows completely). Now click and scroll a bit and find the same post from homepage post listing here:
http://www.sitruunapuu.net/blog/

Note that same image is cropped here in homepage because something is wrong in a way page calls css ie twice? Maybe because in homepage some div classes are twice (div .Post or .content), but how am I supposed to fix it? Not css file… Maybe archive.php? Argh I don’t know…

Please help. Homepage with those cropped images and wide margins looks very nasty.

Thanks!!